Yup, Mk I Chorus Monoplaners: 1988 - 1990.
Mk I had white wheel guide rubbers and white o-rings on the brake adjusters; the casting of the caliper arms (where the pad holders attach) is also different to later versions.
Mk II ('91 - '93) had "naked" wheel guides (from Record) and black o-rings.
I've been on the lookout for a pair of Mk II for a while, so I've got a bit nerdy on Monoplaners.
Also agree that the shifters are from 1992, the triangular ends of the levers are distinctive. Record, Chorus and Athena were all equipped with the same one, EC-02RE CG.